This invention relates to a method of making a core shaft and, more particularly, to a shaft for supporting a roll of paper or the like in either an unwind or a rewind which includes a rack and pinion lock.
Such locks are old and well known--see, for example, U.S. Pat. Nos. 1,122,627; 2,798,678 and 4,158,446. However, such core lock shafts have not been used in connection with computer printers--the field to which the instant invention finds particular application.
For many years, business forms were zig-zag folded by the manufacturer and then stepped through the computer printer and refolded. With the advent of higher speed printers, particularly laser printers, this meant that boxes of folded forms had to be opened and installed every few minutes. This was acceptable for short runs but for longer runs, the art has turned to roll feed to avoid the problems of handling the folded forms.
Conventional art for clamping the core of the roll to the shaft or mandrel included end chucks which, again, required some time for installation and adjustment. Also widely employed were air bags internal of the shaft which expanded dogs or gripping segments and which were expensive and further required the access to compressed air. Although many operating plants have compressed air available, often it turned out that the only reason for using the compressed air was to have the shaft arcuate segments moved radially outward into gripping relation with the core.
The drawbacks have been avoided through the instant invention which employs an axially elongated rack and pinion provided within an opening or recess in the outer wall of the shaft. The inventive method provides a core lock shaft specifically advantageous in connection with computer printers and which costs a few hundred dollars as contrasted to the several thousand dollars involved in the more complicated equipment used currently by the art and which requires special maintenance.
According to the inventive method, a cylindrical shaft having a diameter of about 3" and a length of about 8" is adapted to rotatably support a paper roll having a diameter of up to about 50" and normal widths ranging from 8 to 22". The method includes cutting an axially elongated recess in the shaft periphery to provide a chordal bottom wall in which a plurality of axially extending transverse slots are ground to develop rack teeth. The unexpected economy is provided by using a length of pinion wire having a diameter slightly greater than the depth of the recess and equipping the pinion wire ends with inserted dowel pins. The so-equipped pinion wire is then mounted in the recess with interlacing of the pinion teeth and the rack teeth and clip means installed at the ends of the recess to retain the dowel pin-equipped pinion wire.